Technical Field
The present disclosure is directed to control smart windows with electrochromic (EC) coatings or automated venetian blinds.
Description of the Related Art
The demand for energy has been rising continuously and is likely to continue in the future. British Petroleum published a report on the current status of energy in the world, which shows an increase of 2.3% in the global primary energy consumption as described in BP Statistical Review of World Energy, 2014, the entire contents of which is incorporated herein by reference. Growth in population and the enhancement in building services and comfort levels have increased the building energy consumption as described in International Energy Agency, Key World Energy Statistics 2014, the entire contents of which is incorporated herein by reference. The reduction of energy consumption in buildings can make a significant contribution toward lowering the global demand for energy as described in N. B. Behmiri, J. R. Pires Manso, “How crude oil consumption impacts on economic growth of sub-Saharan Africa,” Int. J. Energy 54 (2013) 74-83, the entire contents of which is incorporated herein by reference.
Office buildings usually emit a high amount of internal heat gain due to high rates of occupancy and significant usage of equipment and lighting as described in J. Choi, A. Aziz, V. Loftness, “Investigation on the impacts of different genders and ages on satisfaction with thermal environments in office buildings,” Build. Environ. 45 (2010) 1529-1535. Office workers depend on the comfortable conditions provided in the building to performing their various tasks. Thus, their productivity is directly dependent on the comfort level provided inside the building as described in A. Gasparella, G. Pernigotto, F. Cappelletti, P. Romagnoni, P. Baggio, “Analysis and modelling of window and glazing systems energy performance for a well-insulated residential building,” Energy Build. 43 (4) (2011) 1030-1037, the entire contents of which is incorporated herein by reference. Office buildings consume a high amount of energy in the form of space cooling/heating and lighting, equipment, water heating, ventilation and other applications as described in H. Hens, “Thermal comfort in office buildings: two case studies commented,” Build. Environ. 44 (2009) 1399-1408, the entire contents of which is incorporated herein by reference. In a typical office building, artificial lighting and cooling/heating/equipment are considered to be major contributors to building energy consumption making these systems the best targets for energy savings as described in P. Ihm, L. Park, M. Krarti, D. Seo, “Impact of window selection on the energy performance of residential buildings in South Korea,” Energy Policy 44 (2012) 1-9, the entire contents of which is incorporated herein by reference. The International Energy Agency has indicated that in a typical office building, artificial lighting consumes the bulk of the energy followed by cooling and heating operations as described in International Energy Agency, Key World Energy Statistics 2014. Office buildings have a relatively high proportion of lighting energy consumption per unit area due to their functional and operational requirements as described in H. Hens, “Thermal comfort in office buildings: two case studies commented,” Build. Environ. 44 (2009) 1399-1408.
In a hot climate, cooling accounts for the highest share of energy consumption in office buildings. Internal heat gain and solar gain through the exterior envelope are the major contributors to the thermal load in an office building. Heat gain through windows in particular represents a significant component of the cooling load and consequently a major contributor to energy consumption as described in T. Berger, C. Amann, H. Formayer, A. Korjenic, B. Pospichal, C. Neururer, R. Smutny, “Impacts of urban location and climate change upon energy demand of office buildings in Vienna, Austria,” Build. Environ. 81 (2014) 258-269, the entire contents of which is incorporated herein by reference. Window glazing plays an important role in energy performance and has a significant effect on the overall building energy consumption. Heat flow through a glazed window contributes to the heat gain due to incident solar radiation which eventually increases the cooling load as described in M. T. Ke, C.-H. Yeh, J.-T. Jian, “Analysis of building energy consumption parameter and energy savings measurement and verification by applying Quest software,” Energy Build. 61 (2013) 100-107, the entire contents of which is incorporated herein by reference. In buildings, the net energy gain through windows depends on the thermal properties of the glazing material. Double-pane coated glass windows are used for reducing heat and energy losses. They are very effective in lowering the building energy consumption by reducing the cooling load when compared with traditional double-glazed clear glass windows. However, colored glazing reduces the admittance of daylight thereby hindering the chances of effective utilization of daylight integration with artificial lighting as described in H. Arsenault, M. Hebert, D. Marie-Claudie, “Effects of glazing color type on perception of daylight quality, arousal, and switch-on patterns of electric light in office rooms,” Build. Environ. 56 (2012) 223-231, the entire contents of which is incorporated herein by reference.
Daylight received through windows can significantly contribute to the reduction of lighting energy consumption in office buildings as described in M. T. Ke, C.-H. Yeh, J.-T. Jian, “Analysis of building energy consumption parameter and energy savings measurement and verification by applying Quest software,” Energy Build. 61 (2013) 100-107. It is considered as a potential passive strategy for reducing the building energy consumption and improving the visual comfort without any expensive operational cost and installation. Y. W. Lim, M. Z. Kandar, M. H. Ahmad, D. R. Ossen, M. A. Abdullah, “Building facade design for daylighting quality in typical government office building,” Build. Environ. 57 (2012) 194-204, the entire contents of which is incorporated herein by reference, is a study with the aim of evaluating the daylighting performance in a typical government office building in Malaysia. Based on the simulation study, they found that by changing the glazing of the windows and adding interior blinds, a significant improvement in daylighting quantity and quality for visual comfort could be achieved. The amount of savings can result from changing the glazing of the window, and the study focused only on the usage of static blinds which block a considerable amount of daylight to maintain visual comfort in the office. H. Shen, A. Tzempelikos, “Sensitivity analysis on daylighting and energy performance of perimeter offices with automated shading,” Build. Environ. 59 (2013) 303-314, the entire contents of which is incorporated herein by reference, investigated the impact of different shading control strategies on the building energy performance and daylighting in an office space using year-round, transient, thermal- and lighting-integrated simulation. Interior shades were used to block solar radiation and improve the visual comfort by suppressing the glare for the occupants inside the building. Four different shading control strategies were modeled for maximizing the daylight utilization, minimizing energy consumption, and reducing the risk of visual discomfort. The role of automated roller shades was also addressed in improving the energy and visual performance in an office building without considering the impact of different glazing types.
Daylighting provides a pleasant and attractive indoor environment that can foster higher productivity and performance as described in P. Plympton, S. Conway, K. Epstein, “Daylighting in Schools: Improving Student Performance and Health at a Price Schools Can Afford,” National Renewable Energy Laboratory Report, CP-550-28059, Golden, Colo., 2000, the entire contents of which is incorporated herein by reference. With the proper use of sensors and controllers, daylighting is capable of reducing the electrical lighting and providing sufficient illuminance levels inside an office space. Y. W. Wong, “Energy performance of office building in Singapore,” ASHRAE Trans. 94 (Part (2)) (1988) 546-559, the entire contents of which is incorporated herein by reference, describes a numerical study for an office building located in the tropical climate of Singapore city and concluded that, with proper daylight integration, the amount of energy savings can be increased by lowering the lighting expenditure and the cooling energy consumption. D. H. W. Li, J. C. Lam, “Evaluation of lighting performance in office buildings with daylighting controls,” Energy Build. 33 (2001) 793-803, the entire contents of which is incorporated herein by reference, describes a study that indicated that, due to the limited studies in the field of daylighting, many architects and building owners are reluctant to invest in daylighting control strategies.
As discussed above, the available literature shows that work has been conducted by researchers in exploring the benefits of daylighting, but in most of these studies the visual comfort component was ignored. Visual comfort is very important in an environment where the employees work continuously, as it can affect the employee's productivity level. Visual comfort is created with a predetermined amount of good quality light and a sophisticated light distribution. Assessing visual comfort in a critical indoor environment such as an office building is a challenging task. Many parameters must be considered during the calculations, inside an office building.
Different commercially available glazed windows were assessed and energy savings associated with each window design were identified with and without daylight integration. Too much daylight can provide excessive luminance and create an uncomfortable working environment causing visual discomfort as described in X. Yu, Y.h. Su, H.f. Zheng, S. Riffat, “A study on use of miniature dielectric compound parabolic concentrator (dCPC) for daylighting control application,” Build. Environ. 74 (2014) 75-85, the entire contents of which is incorporated herein by reference. Proper design considerations can be employed when selecting the glazing of the window to ensure maximum daylight with minimal glare index as described in U. Berardi, T. Wang, “Daylighting in an atrium-type high performance house,” Build. Environ. 76 (2014) 92-104, the entire contents of which are incorporated herein by reference.